The old plantation where Michelle Obama's great-great-grandfather lived is tucked behind the tire stores and veterinary clinics of U.S. Highway 521. But its history and grounds have been meticulously preserved, down to the dikes that once controlled the flow of water into its expansive rice fields.

Not much is known about Jim Robinson, however, including how or when he came to Friendfield, as the property is still called. But records show he was born around 1850 and lived, at least until the Civil War, as a slave. His family believes that he remained a Friendfield worker all his life and that he was buried at the place, in an unmarked grave.

Until she reconnected with relatives here in January on a campaign trip, Obama did not know much about her ancestry, or even that Friendfield existed. As she was growing up in Chicago, her parents did not talk about the family's history, and the young Michelle Robinson didn't ask many questions.

But if her husband is elected president in November, he will not be the only one in the family making history. While Barack Obama's provenance -- his black Kenyan father, white Kansas-born mother and Hawaiian childhood -- has been celebrated as a uniquely American example of multicultural identity, Michelle Obama's family history -- from slavery to Reconstruction to the Great Migration north -- connects her to the essence of the African American experience.

To Rep. James E. Clyburn (D), whose district includes part of Georgetown County, the possibility that a descendant of slaves could be first lady is just as momentous as the prospect of a black man as president. "I believe she could play as pivotal a role as her husband could, if not more so. It would allow us an opportunity to get beyond some of our preconceived notions, some of our prejudices," he said.

Those who have studied African American history believe Michelle Obama's prominence could help bring to light the complexities of what Southern whites once called the "peculiar institution," now regarded as an indelible stain on the American conscience.

"It's good to be a part of playing out history in this way," Obama said in an interview at the campaign's Chicago headquarters. "It could be anybody. But it's us, it's our family, it's that story, that's going to play a part in telling a bigger story."

It is a process, she continued, of "uncovering the shame, digging out the pride that is part of that story -- so that other folks feel comfortable about embracing the beauty and the tangled nature of the history of this country."

Early this year, before Obama traveled to Georgetown to help her husband in the South Carolina primary, campaign aides began to interview her relatives and scour genealogical records, not sure of what they would discover. Later they enlisted help from historians to produce a detailed Robinson family tree.

Sheryll Cashin, a Georgetown University law professor and author of a book about her own Alabama family, says that for African Americans, there is nothing unique about the Robinson family. "I would venture to say that this is not an extraordinary story," said Cashin, a friend of Obama's. "It's an extraordinary story because it's been unearthed."

The Obama campaign agreed to cooperate for this article, as did Robinson family members who live in Georgetown and had previously declined all interview requests. Many had known parts of their family history but not the full odyssey, including details unearthed by The Washington Post in its own inquiries.

Obama said that what she has learned about her family has helped her understand more about her upbringing as well as the scars of slavery that many African Americans still bear.

"A lot of times these stories get buried, because sometimes the pain of them makes it hard to want to remember," she said. "You've got to be able to acknowledge and understand the past and move on from it. You have to understand it, and I think a lot of us just don't have an opportunity to understand it -- but it's there."

South Carolina Roots

Most Sunday evenings during her childhood, Michelle Robinson and her parents, Marian and Fraser Robinson III, visited her grandparents at their house nearby. Michelle's father was born in Chicago and spent his career working for the city, tending the boilers at a water-filtration plant. But her grandfather, Fraser Jr., often reminisced about his South Carolina childhood. The little girl listened and tried to read between the lines.

Fraser Robinson Jr.'s trek north to Chicago was one that millions of Southern blacks took over several generations, altering the racial landscape on both sides of the Mason-Dixon line. But the move did not deliver on its promise. Robinson landed a dull but reliable Postal Service job. By the time Michelle's parents were married, Robinson and his wife, LaVaughn, were living in a cinderblock apartment in a public housing project -- a tidy complex, as Michelle remembers it, but humble compared with the house that her grandfather's father, Fraser Sr., had built in South Carolina.

"He was a very proud man. He was proud of his lineage," Obama recalled. However, she added, "there was a discontent about him."

No one in the family was surprised when the couple moved to Georgetown after they retired. Fraser and LaVaughn Robinson joined Bethel AME Church, where the Robinson family had worshiped since the turn of the century. They celebrated their 50th wedding anniversary at a local veterans hall with Robinson cousins and old school friends.

Starting when she was 10 years old, Obama was a regular visitor to Georgetown. She remembers the crickets that kept her awake at night and the fresh venison that made her ill. She passed countless times by the Friendfield gate but never noticed the dirt road, much less where it led. For a family that otherwise loved to engage, "we didn't talk about that," she said.

An hour northeast of Charleston in the Low Country region, Georgetown County was settled in early Colonial days. By the mid-1800s, thousands of slaves worked its snake- and mosquito-infested riverfront fields, producing half of the rice consumed in the United States.

Friendfield thrived for a century as a productive plantation, but its fortunes collapsed after the Civil War. The rice mill burned, the grand house was looted, and smallpox ravaged white and black households alike. Many of Friendfield's former slaves continued to live on the property as sharecroppers, in a community known as the Hill that included a church and a clinic.

One Friendfield worker during this period is believed to have been Jim Robinson. He appears in the 1880 Census, recorded as an illiterate farmhand living in close proximity to the plantation's white owners. He was married with a 3-year-old son, Gabriel. A second son, Fraser, Michelle Obama's great-grandfather, was born in 1884.

Gabriel Robinson's daughter Carrie Nelson, now 80, is the oldest living Robinson and the keeper of family lore. Before Obama's January visit, Obama cousins Connie Jones and Harolyn Siau called on Carrie to help piece together the family history.

Seated in an easy chair in the living room of her small ranch-style house, Nelson relied on a tattered family Bible and a long and lively memory to reconstruct the final days at Friendfield, recalling stories her father had told her as a girl. Jones, who grew up in town but remained close to her country cousins, listened raptly from the sofa, interjecting with "Really?" and "I never knew," as Nelson's family narrative unfolded.

When Gabriel and Fraser Robinson were young, their mother died and Jim remarried. When Fraser was about 10, Nelson recounted, he ventured into the woods to collect firewood, and "a little sapling fell on his arm and it broke." His stepmother brushed off the injury. But the wound became infected, and Fraser's left arm had to be amputated.

One witness to the tumultuous Robinson family scene was a white man named Francis Nesmith, the son of an overseer at another plantation and a regular visitor to Friendfield. As Gabriel Robinson told his daughter, Fraser would tag along with Nesmith, and Nesmith grew fond of the one-armed boy. Aware of Fraser's difficult home life, Nesmith asked Jim Robinson if the boy could come live with him.

"He said he would take good care of him, and he did," Nelson said. "Uncle Fraser and that man's children grew up together."

In the 1900 Census, Fraser is listed as a "house boy" living with the Nesmith family. At 16, he could not read or write. But the Nesmith children attended school, and their parents were literate. That left an impression on her uncle, Nelson said.

"They pushed their kids hard into education, and one day Uncle Fraser would, too, because that's what he learned from them," she said of the Nesmiths.

Keenly aware of his wife's heritage, Barack Obama has called Michelle "the most quintessentially American woman I know." During his speech on race in Philadelphia this spring, he noted, "I am married to a black American who carries within her the blood of slaves and slave owners."

A white ancestor has long been an assumption in the Robinson family, but there is no evidence of who it was. It is something Michelle Obama would like to know; but even with that still a mystery, she draws a lesson from her family history.

"An important message in this journey is that we're all linked," she said. "We are in fact, through our histories of growth and survival in this country. Somewhere there was a slave owner -- or a white family in my great-grandfather's time that gave him a place, a home, that helped him build a life -- that again led to me. So who were those people? I would argue they're just as much a part of my history as my great-grandfather."

Getting Ahead

Jim Robinson's sons prospered. Gabriel joined a turpentine crew and bought a farm west of Friendfield, a portion of which remains in the family. Fraser married Rosella Cohen, taught himself to read and worked as a shoemaker and a newspaper salesman in addition to a lumber mill job.

Dorothy Taylor, 89, who lives a block from Bethel AME and keeps an Obama picture book on her coffee table, recalls watching "Mr. Fraser Robinson" selling the local paper on a downtown street corner. All the students at Howard School, the county's only black high school, knew he took spare copies home each night so his children could read them.

"It was the belief that education was our salvation -- education and religion," Taylor said. "You've got to trust in God and learn all you can. Because we had meager lives. We had nothing."

Obama's grandfather was born in 1912. He was a standout student and was known as an orator, but at 18, census records show, Fraser Robinson Jr. was living at home with his parents and working at a local sawmill. It was a time when Georgetown blacks were losing the legal rights and social status they had started to gain after emancipation, and the local economy was in shambles.

"There were no jobs here," said Harolyn Siau, a Robinson cousin and retired teacher. "I guess a man who thought like he thought, he wouldn't want to do ordinary stuff." A Robinson family friend had moved to Chicago, and Fraser Robinson Jr. decided to follow him -- at least for a while.

The Time Has Come?

When the Obama campaign began compiling the Robinson genealogy, aides had no idea what they might find. And Michelle Obama still knows very little about her other grandparents, although she was told LaVaughn was a Mississippi preacher's granddaughter.

But the Robinson story says plenty. At least three of Fraser Sr.'s sons -- Michelle Obama's great-uncles -- joined the military. One daughter moved to Princeton, N.J., where she worked as a maid, and she cooked Southern-style meals for Michelle and her brother, Craig, when they were students at Princeton University.

Connie Jones's father, Thomas Robinson, served for 25 years as the beloved principal of an elementary school in an African American community that had formed near the Friendfield property line.

"It makes more sense to me," Obama said. "If the patriarch in our lineage was one-armed Fraser, a shoemaker with one arm, an entrepreneur, someone who was able to own property, and with sheer effort and determination was able to build a life in this town -- that must have been the messages that my grandfather got."

In January, Obama spoke at Bethel AME to a packed crowd that included at least 30 family members. Word spread quickly through the Robinson clan that one of their own could be White House bound. "God is absolutely amazing!" Thomas Nelson, a cousin who works at Robins Air Force Base in Georgia, wrote in an entry posted on the Obama campaign blog.

And yet there is a wariness about delving too deep. Relatives, including Jones and Siau, have been approached by scores of reporters, but they are uneasy about speaking about their cousin for fear of stoking racial tensions and damaging her husband's chances.

Scholars of slavery and the South believe Obama could become a catalyst for allaying such fears. "It could play out in a dozen different ways, but there's no question that people are now ready to hear this," said Peter H. Wood, a Duke University history professor and an expert on the antebellum South. "They're ready to hear that she's proud, not ashamed, and how she can make other people feel okay about it.

"So she becomes, in some ways, the Alex Haley of her generation," Wood said, referring to the author who traced his African ancestry in the celebrated novel "Roots."

On that trip in January, Obama drove by Friendfield, just as she did when she was a girl, but this time she looked out the car window and noted the historic marker. Next time she's in town, she said, she would like to see the place.

"There are probably thousands of one-armed Frasers, all over this country," she said, "who out of slavery and emancipation, because they were smart and worked hard, those American values, were able to lift themselves up and begin to set these little foundations that led to me."